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Simulators >> Circuit Simulators >> operating point info in MDL?
https://designers-guide.org/forum/YaBB.pl?num=1170344257

Message started by topquark on Feb 1^st, 2007, 7:37am

Title: operating point info in MDL?
Post by topquark on Feb 1^st, 2007, 7:37am

Hello folks,

While I'm able to plot all sorts of expressions(using calculator functions) defined in my MDL script, I find it puzzling to get operating point info like gm, Vth etc..
While these are present in the psf dump of the Analog Design Environment, I can't see a similar thing in the .raw o/p of the MDL

Plz share any ideas people!

Thanks,
Gau

Title: Re: operating point info in MDL?
Post by topquark on Feb 3^rd, 2007, 4:24am

well, i know it's weekend..but, just in-case any of you scripting experts logged in :P
care to help me out!
This thing's been bugging me..

The idea is to be able to plot, say threshold voltage of a device Vth as a function of sweeping supply VDD. I'm aware I can do this as a paramteric analysis in ADE but, I'm hampered by limited measurement capabilites therein.
So, I write this MDL script to do some measurements involving VDD as a variable which keeps changing during each sweep.

Have you folks used a syntax to get a device's operating point info like Vth, gm in MDL?
Appreciate your comments

Ciao
Gau

Title: Re: operating point info in MDL?
Post by Scott Flinchbaugh on Feb 5^th, 2007, 7:04pm

Gau,

There are a couple of ways to accomplish this.

The most desired way is to embed this information into your "alias measurement" with statements such as:

export real myvth = <devicename>:vth

Or in a more generic fashion:
export real <MDLparamname> = <devicename>:<device_parametername>

To obtain the operating point data for a device, you simply need to access the device's op output parameter.
This will place the MDL variable "myvth" into the .measure file generated by MDL and will also place it
into the psf files generated by MDL.

Another way to do this is to use the Spectre save statement here. The syntax is a bit different:
save <devicename>:<device_parameter>

Hope this helps,
-scott

Title: Re: operating point info in MDL?
Post by topquark on Feb 6^th, 2007, 12:35am

Hey Scott
Thanks pal.. that was very helpful indeed!!

Just another particular though-
For e.g you want vth of a pmos device MP1, you will have to write the MDL statement as

export real myvth = MP1.m1 : vth

Without .m1 , the script still runs without errors but doesn't output vth of the required device.

The same applies to even the save statement in spectre.

Cheers,
Gau

Title: Re: operating point info in MDL?
Post by Geoffrey_Coram on Feb 6^th, 2007, 6:53am

topquark wrote on Feb 6^th, 2007, 12:35am:

export real myvth = MP1.m1 : vth

Without .m1 , the script still runs without errors but doesn't output vth of the required device.

That's almost certainly because MP1 is a subckt in your library, and the actual device is "m1"